The marketplace review is being handled through AAR.
The brand currently works with Wieden & Kennedy Amsterdam and AKQA, both of which are unaffected by the review.
In March Booking.com revealed its "booking hero" campaign in the UK with a spot called "booking right". It featured a man getting his holiday accommodation right which led to him having a happy life.
The brand launched its first UK ad campaign at the beginning of last year called "booking epic". Wieden & Kennedy Amsterdam picked up the account in 2012. Before this Booking.com handled online advertising in-house for 15 years.
The company is part of The Priceline Group, an online travel company. Booking.com was established in 1996 and is headquartered in Amsterdam with 173 offices across 60 countries.
Booking.com declined to comment.